The maximum high tide occurs under the following key conditions:

• Alignment of the Sun, Moon, and Earth: When the Sun and Moon are aligned with the Earth during a new moon or full moon (a configuration called syzygy), their gravitational forces combine and reinforce each other, producing higher than normal tides known as spring tides

• Moon's proximity to Earth (Perigee): When the Moon is closest to Earth in its elliptical orbit (perigee), the tidal forces are stronger, resulting in higher tides. When perigee coincides with a new or full moon, it causes perigean spring tides , which have the largest tidal ranges

• Geographical and coastal features: The shape of the coastline and ocean basin can greatly amplify tidal heights. Funnel-shaped bays or estuaries, such as the Bay of Fundy in Canada, concentrate tidal waters and produce some of the world's highest tides, exceeding 15 meters in height

• Local ocean depth and topography: Shallow coastal waters and continental shelves tend to enhance tidal ranges by restricting water flow and causing tides to build up higher than in deep ocean basins

• Meteorological conditions: Low atmospheric pressure allows sea levels to rise (inverted barometer effect), and strong onshore winds can push water toward the coast, both increasing the actual high tide level beyond astronomical predictions. Storm surges, combining wind and pressure effects, can further raise tide levels significantly

In summary, the maximum high tide occurs when the Sun and Moon are aligned during a new or full moon, the Moon is near perigee, and local coastal geography and meteorological conditions favor amplification of tidal heights. This combination leads to the highest tidal bulges and thus the maximum high tide at a given location